The invention is particularly well suited for building low pressure, flotation type tires which are generally used on amphibious type vehicles. Moreover, the invention is designed for use in the casting, or injection molding of tires, and especially centrifugally casting polyurethane rubbery material around a network of conventional tire reinforcement cords.
Most pneumatic tires are cast, or injection molded in a toroidal configuration, as shown in U.S. Pat. No. 3,458,373. This particular patent shows and describes injecting tire forming material around a preformed, basket-like reinforcement structure braided from organic, or inorganic wire, or from thermoplastic synthetic resins, as distinguished from individual tire cords normally used in the reinforcement of tires built by more conventional methods using plies of rubbery material reinforced with such cords. It can be easily imagined that it is extremely difficult maintaining the individual tire reinforcement cords in toroidal pathways during the casting, or injection molding process, since the cords are easily pushed from their desired pathways by the material as it flows into the mold. Moreover, the cords contact the inner core of the mold, if spacers are not used for maintaining the cords free of the core. This is evidenced by the aforementioned patent which shows and describes the use of a number of spacers for holding the basket-like structure free of the inner core of the mold. The invention is directed to solving this particular problem.
Briefly stated, the invention is in an improved method of casting, or injection molding a tire. Similarly dimensioned lengths of conventional tire cords are held cylindrically in parallel array while a suitable tire forming material is cast, or injection molded around the cords to form a cylindrically shaped tire which is then cured in the cylindrical configuration.